Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $106.41   11.628%   $118.7834   $118.78   $118.80   $118.80  
  Purchase #2 $23.89   12.147%   $26.7919   $26.79   $26.80   $26.80  
  Purchase #3 $246.48   9.526%   $269.9597   $269.96   $269.95   $270.00  
  Purchase #4 $243.79   9.742%   $267.54   $267.54   $267.55   $267.50  
  Purchase #5 $117.99   7.536%   $126.8817   $126.88   $126.90   $126.90  
  Purchase #6 $223.95   10.457%   $247.3685   $247.37   $247.35   $247.40  
  Purchase #7 $51.54   6.362%   $54.819   $54.82   $54.80   $54.80  
  7 purchase totals = $1,014.05       $1,112.1442   $1,112.14   $1,112.15   $1,112.20